ABSTRACT: The dog is an ideal large animal model for diagnostic and therapeutic studies and can be used to translate successes to human patients while providing compassionate care to animals and advancing the field of veterinary medicine. Pet dogs share their environment, and oftentimes their diet, with their owners. Dogs and humans develop sporadic benign and malignant brain tumors at about the same rate and with similar histopathology. Dogs are often euthanized due to the cost of care. Thus, the spontaneously occurring canine brain tumor represents an ideal opportunity to improve the lives of people as well as pets through comparative oncology and genomics and the ?One Medicine? approach to research and direct clinical application. We propose a multi-institutional consortium to test an innovative combinatorial immunotherapeutic approach in dogs that spontaneously and sporadically develop malignant glial brain tumors that resemble in most important aspects, high-grade malignant gliomas in humans. Our approach will inject a clinical grade oncolytic herpes simplex virus (HSV) M032 that expresses human interleukin-12 (IL-12) into the resected tumor bed. Dog lymphocytes fully respond to human IL-12 [1] and oncolytic HSV infect and kill canine (as well as mouse, non-human primate, human) tumor cells, creating a potent local inflammatory response and an antigen-rich tumor cell debris field. Therefore, we would anticipate that this virally-based immunotherapeutic approach would likely be as effective in dogs with brain tumors as in humans with brain tumors. We will conduct longitudinal safety, survival and correlative biology evaluations as a means of assessing the dog as an appropriate and informative model for design and implementation of clinical studies in humans with high-grade malignant brain tumors. To extend these findings, we propose, in subsequent studies, to combine the HSV immunotherapy approach with molecules that block the action of innate checkpoint inhibitor(s). These studies are designed to address key issues of safety and efficacy of combinatorial immunotherapy in the dog that can be translated to humans with malignant gliomas. Malignant gliomas are the most common primary brain tumors in humans, accounting for 30% of all primary central nervous system (CNS) tumors in adults. [2] With few major advances in decades, there has been no significant reduction in mortality and only a modest improvement in median survival. Recently, objective responses and long-term survivals have been observed in human glioma patients who have received oncolytic virotherapy and a Phase I trial is currently underway at UAB in patients using M032 alone. New approaches to utilize checkpoint inhibitors promises improved efficacy, but the ability to develop more effective combinatorial approaches has been slow, in large part due to lack of a faithful model of spontaneous glioblastoma multiforme (GBM) in immunocompetent hosts. Thus, the spontaneously occurring canine brain tumor represents an ideal opportunity to improve the lives of people and pets through comparative oncology and genomics using the ?One Medicine? approach to research and direct clinical application.